Safe methods vs unsafe methods in Rest API - Practice Questions

Challenge - 5 Problems

🧠 Conceptual

intermediate

Which HTTP method is considered safe?

In REST APIs, safe methods are those that do not change server data. Which of the following HTTP methods is safe?

A POST

B PUT

C GET

D DELETE

💡 Hint

Safe methods are used only to retrieve data without side effects.

GET is a safe method because it only retrieves data and does not modify any resource on the server.

🧠 Conceptual

intermediate

Which HTTP method is unsafe and used to update resources?

Unsafe methods can change server data. Which HTTP method below is unsafe and typically used to update an existing resource?

A GET

B HEAD

C OPTIONS

D PUT

💡 Hint

Updating means changing data on the server.

PUT is unsafe because it modifies or replaces the resource on the server.

❓ Predict Output

advanced

What is the output status code for a safe GET request?

Consider this HTTP request made to a REST API endpoint that returns data without changing anything. What is the typical HTTP status code returned?

Rest API

GET /api/items/123 HTTP/1.1
Host: example.com

A 200 OK

B 201 Created

C 204 No Content

D 400 Bad Request

💡 Hint

Successful GET requests usually return the requested data.

A 200 OK status means the GET request succeeded and the server returned the requested data.

❓ Predict Output

advanced

What error occurs if a DELETE method is sent to a read-only API?

If you send a DELETE request to an API that only allows safe methods, what HTTP status code will the server most likely return?

Rest API

DELETE /api/items/123 HTTP/1.1
Host: example.com

A 405 Method Not Allowed

B 200 OK

C 500 Internal Server Error

D 404 Not Found

💡 Hint

The server rejects methods it does not support.

405 Method Not Allowed means the server understands the method but refuses to allow it on the resource.

🧠 Conceptual

expert

Why are safe methods important for caching in REST APIs?

Safe methods like GET are often cached by browsers and proxies. Why is caching safe methods important in REST API design?

A Because safe methods always modify data, caching prevents repeated changes.

B Because safe methods do not change data, caching their responses improves performance without risk of stale data.

C Because unsafe methods are cached to reduce server load.

D Because caching safe methods causes data corruption.

💡 Hint

Think about how caching helps when data does not change.

Safe methods do not change data, so their responses can be cached safely to speed up repeated requests without causing incorrect data to be shown.

Practice

1. Which HTTP method is considered safe because it only retrieves data without changing anything?

easy

A. DELETE

B. POST

C. PUT

D. GET

Solution

1. Step 1: Understand safe methods

   Safe methods do not change data on the server; they only read or retrieve data.

2. Step 2: Identify the safe method among options

   GET is the method used to request data without modifying it, making it safe.

3. Final Answer:

   GET -> Option D

4. Quick Check:

   Safe method = GET [OK]

Hint: Safe methods only read data, GET is the common safe method [OK]

Common Mistakes:

• Confusing POST as safe
• Thinking PUT is safe
• Assuming DELETE is safe

2. Which of the following is the correct syntax to send data to a server to create a new resource?

easy

A. POST /resource HTTP/1.1

B. GET /resource HTTP/1.1

C. DELETE /resource HTTP/1.1

D. PUT /resource HTTP/1.1

Solution

1. Step 1: Identify method for creating resources

   POST is used to send data to the server to create new resources.

2. Step 2: Check syntax correctness

   POST /resource HTTP/1.1 is the correct syntax to send data for creation.

3. Final Answer:

   POST /resource HTTP/1.1 -> Option A

4. Quick Check:

   Creating resource = POST [OK]

Hint: POST is for sending data to create, syntax includes POST and resource path [OK]

Common Mistakes:

• Using GET to send data
• Confusing DELETE with POST
• Using PUT for creation without context

3. What will be the result of this HTTP request method usage?

PUT /items/123 HTTP/1.1
Content-Type: application/json

{"name": "New Item"}

Choose the correct description.

medium

A. It retrieves the item with ID 123 without changes.

B. It updates or replaces the item with ID 123 with new data.

C. It deletes the item with ID 123 from the server.

D. It creates a new item without specifying an ID.

Solution

1. Step 1: Understand the PUT method purpose

   PUT is used to update or replace an existing resource at a specific URL.

2. Step 2: Analyze the request details

   The request targets /items/123 with JSON data, meaning it updates item 123.

3. Final Answer:

   It updates or replaces the item with ID 123 with new data. -> Option B

4. Quick Check:

   PUT updates resource = C [OK]

Hint: PUT replaces or updates resource at given URL [OK]

Common Mistakes:

• Thinking PUT retrieves data
• Confusing PUT with DELETE
• Assuming PUT creates without ID

4. Identify the error in this HTTP request if the goal is to safely retrieve data:

POST /users HTTP/1.1
Host: example.com

medium

A. The HTTP version is incorrect; it should be HTTP/2.0.

B. The Host header is missing, causing a syntax error.

C. POST is unsafe and changes data; GET should be used to retrieve data.

D. POST cannot be used with /users endpoint.

Solution

1. Step 1: Understand the goal and method used

   The goal is to safely retrieve data, but POST is used which changes data.

2. Step 2: Identify correct method for safe retrieval

   GET is the safe method to retrieve data without side effects.

3. Final Answer:

   POST is unsafe and changes data; GET should be used to retrieve data. -> Option C

4. Quick Check:

   Safe retrieval = GET, not POST [OK]

Hint: Use GET to retrieve data safely, not POST [OK]

Common Mistakes:

• Ignoring method safety
• Thinking Host header is missing
• Confusing HTTP versions

5. You want to design an API endpoint that allows clients to delete a user account safely. Which HTTP method should you use, and why?

hard

A. DELETE, because it explicitly removes the resource on the server.

B. POST, because it can send data and create resources.

C. GET, because it is safe and does not change data.

D. PUT, because it updates existing resources.

Solution

1. Step 1: Identify the action needed

   The goal is to remove (delete) a user account from the server.

2. Step 2: Choose the correct HTTP method for deletion

   DELETE is the method designed to remove resources safely and clearly.

3. Final Answer:

   DELETE, because it explicitly removes the resource on the server. -> Option A

4. Quick Check:

   Deleting resource = DELETE method [OK]

Hint: Use DELETE to remove resources explicitly and safely [OK]

Common Mistakes:

• Using GET for deletion
• Confusing POST with DELETE
• Using PUT instead of DELETE